Static stretching: beyond the noise.

Namaste

Jul 03, 2020

This post takes a deep dive into something so omnipresent that it might be considered blasphemous to even question its utility. Hoards of people so religiously do it that one might believe it to be entrenched in our cultural identity. Hell, even dogs and cats do it, with some poses being named after these animals. If the title hasn’t already given it away, you’d be hard pressed to think that I'm alluding to static stretching.

Growing up I was always told to stretch whenever I had any pain. Shoulder hurts? Stretch. Sore after training? Stretch. Muscle strain? Stretch. Oh you’re injured?! Probably because you didn’t stretch. Stretching was prescribed as a panacea for all ailments physical. It took me a long time to realise that stretching wasn’t worthy of its hallowed repute. Before you haplessly fall victim to any fear mongering like me, let me first dissect what static stretching does or does not do, and then contextualise it for the tennis player.

What is static stretching?

Every muscle has an origin and an insertion. Let’s call it point A and point B. When you static stretch, you increase the distance between points A and B, holding this elongated position until you get bored or spew every pejorative known to man. Chances are you’re thinking of touching your toes.

I always thought that if you took a ruler to a muscle and measured its length after stretching, the reading would increase and said increase would be permanent. Surely I’m not the only one who got sold on the “muscles are like rubber bands” analogy. Au contraire, muscles don’t deform (lengthen) permanently when stretched for longer. To reason why, you need to understand two definitions.

Elasticity - ability of a material to return to its original state once stress/force is removed.
Viscosity - ability of a material to resist a change in shape/ resistance to deformation.

Muscles exhibit both these properties and are said to be viscoelastic. Unlike elastic materials that immediately return to their original shape, viscoelastic materials (your muscles) have time-dependent properties and don’t immediately return to their original state. Therefore, how your muscles responds to a stretch depends on how quickly they’re stretched and for how long they’re stretched. Nonetheless, this increase in viscoelasticity is only temporary and a muscle returns to its original length shortly. Further, there’s no evidence that points to plastic deformation or a permanent change in length as a result of stretching.

In 10 studies that suggested plastic, permanent, or lasting deformation of connective tissue as a factor for increased muscle extensibility, none of the cited evidence was found to support this classic model of plastic deformation. (Weppler CH, Magnusson SP 2010)

What happens when you get desperate and yank on your tissues more than they can tolerate? While over-elongating your connective tissues is extremely hard due to their toughness and resilience, it is not impossible. A mere 4% elongation has been shown to cause micro tears and tissue damage. By over-elongating, you decrease the ability of your connective tissues to withstand load.

Bottomline: Prioritise consistency over intensity. Changes in flexibility come from slow, consistent application, and staying patient is key to noticing long-term improvements.

Ask a tennis player why they stretch and you’ll get the following responses:

A. I stretch to become more flexible.

To make sure you and I are on the same page as to what flexibility is, it needs to be defined. Flexibility is defined as Range of Motion (ROM) around a joint. There are several factors that can affect movement around a joint; not just your muscles’ elasticity. Tendons, ligaments, fascia, skin, joint capsule, bone geometry, age and gender all affect flexibility, and blaming your muscles for lack of flexibility would be quite a stretch (pun intended).

When someone tells me they want to become more flexible, my answer is usually “flexibility for what? How flexible does your sport need you to be?”. I’ve never understood society’s flexibility fetish, with some reputed bodies like ACSM even classifying flexibility as one of the five major components of physical fitness. Almost always, flexibility is measured by the heavily bastardised sit-and-reach test, which begs the question “why do people only give a shit about touching their toes?”. If a player can touch their toes but can’t get their arms fully overhead, do they have good flexibility? Yes, if we take such tests seriously. Interestingly, Eliud Kipchoge, the only man to run a marathon in under two hours, can’t seem to touch his toes. Are we to discredit his fitness levels now? I’m willing to go so far as to say that being unable to touch his toes helped his cause. Here’s an excerpt from the Sweatelite team on Kipchoge.

He was extremely inflexible. After an easy morning run (16km in 1hr10mins), we stretched with the group. Most of them were fairly flexible in the hamstrings (ie. standing straight legged and bending over to touch your toes with your knees straight and being able to touch your toes) but Eliud could only reach to about half way down his shins. He was nowhere near touching his toes! They all found it hilarious that he couldn’t come close to touching his toes.

In my opinion, flexibility is not about having freaky joint ROM but rather being able to exercise control over normal ranges of motion. It might look cool to rip a backhand while doing the full splits, but it makes no sense to do so if you can’t get out of the position safely. Somewhat ironically, the Australian ballet encourages their dancers to strength train with full ROM exercises rather than spend time stretching. This coming from a sport contingent on their dancers having intimidating levels of flexibility should surely give you perspective as to how overblown the requirement for flexibility is.

A recent paper boldly calls for the retiring of flexibility as a major component of fitness and it’s de-emphasis in exercise prescriptions for most populations.

Retirement of flexibility as a major component of physical fitness will simplify fitness batteries; save time and resources dedicated to flexibility instruction, measurement, and evaluation; and prevent erroneous conclusions about fitness status when interpreting flexibility scores. (Nuzzo 2020)

Before this begins to sound like a harangue, let me shed some positive light on stretching. Stretching can increase flexibility. You can achieve greater end ranges by stretching. Here is usually how that happens.

Think of your nervous system as an over-protective mom who knows what’s good for her kid (your muscles). Your nervous system (mom) will not let your muscles (kid) venture (stretch) beyond a limit it considers potentially dangerous. However, the more you stretch, the more lenient your nervous system becomes and allows you to venture a little further until a new suspected danger point is reached. This is called stretch tolerance.

Now, how important an increase in flexibility is depends on how limited your current ROM is. Say you have a flexibility limitation that you need to work on. How much time do you spend stretching? How intense should the stretch be? Which stretch works best? Here’s the unfortunate truth - NO ONE KNOWS.

A Few Good Men - Jack Nicholson - You want the truth? You can't handle the truth.

Fortunately, there are a few guidelines you can follow:

While stretching, you shouldn’t be able to contemplate the meaning of life nor should you have tears rolling down your face. The right intensity seems to be somewhere in between. Much like watching a foreigner eat at an Indian buffet, it needs to be uncomfortable but not painful. Push to the end of your comfort zone.
More does seem to be better. Higher weekly frequencies seem to result in greater ROM improvements, although this could just be a function of higher volumes. As for how long you need to hold a stretch, it doesn’t seem to matter as long as total time is equated. You can do 2 sets of 60 seconds or 4 sets of 30 seconds or 1 set of 120 seconds. Whatever floats your tolerance.

Conclusion: As a tennis player you probably don’t care if the increase in flexibility is a result of decreased stiffness, increased muscle length or nervous system trickery, and that’s fine. What you should care about is stretching with a purpose. Unless you have much to benefit from the increased ROM, don’t waste your time. If you do, devote a couple of minutes everyday rather than consolidating all your stretching into one weekly session. Make a habit out of it. It might look cool to contort yourself like Baba Ramdev, but it might not be the best thing for your tennis.

B. I stretch to warm up and thereby improve performance.

The goal of a warm-up should be to decrease injury risk and/or enhance performance. I don’t eat meat but I know that tugging on a piece of meat doesn’t cook it. I also know that boiling meat makes it more tender and supple. The point I’m trying to make is that warming up does more for your ability to stretch than stretching does for your ability to warm-up. Higher temperatures affect the viscoelasticity of your muscles, which means the warmer a muscle is, the more it can be elongated before tissue damage begins to occur.

The current scientific consensus points to static stretching not having any significant effect on performance, and some trends even indicating deleterious effects. Static stretching has been demonstrated to compromise muscle activation, force production and power output (things you don’t want to lose out on). However, many of the studies used artificial stretching protocols like holding a stretch for longer than 2 minutes, which i’ve never seen any player do in practice. Static stretching when done for durations under 60 seconds show no performance impairments. Further, any performance decrements seem to be negated after a short period of rest or when followed by a more dynamic warm up.

Takeaway: You can static stretch as part of your warm-up. Make sure to keep the intensity low and the duration short (<30 seconds). I personally used to static stretch any muscle that I “perceived” to be tight for very short bouts before I progressed to more dynamic activities. Don't let static stretching be the only warm-up you do or the last thing you do before stepping on court. Since your muscles elongate better when warmer, stretch after your aerobic work, if needed.

C. I stretch to alleviate soreness.

Delayed onset muscle soreness or DOMS is that dull, achy, tender feeling that might leave you feeling “stiffer” than normal. Note that I’ve used the word stiff in quotes. Like I’ve previously mentioned, the feeling of tightness or stiffness is just a feeling, a perception, a sensation. Tightness doesn’t mean that our muscles are actually short. While truly short muscles offer less extensibility, the chances that you have short muscles are slim, and even slimmer are the chances of stretching increasing muscle length. Most often when we stretch, the distance between points A & B stays the same. Any increase in your muscles’ extensibility (ability to elongate) stems from an increase in pain tolerance. In other words, any increase in flexibility in the days after stretching is due to alterations in your nervous systems’ perception of pain and not alterations in your muscles’ length. Further, the relationship between DOMS and muscle length is pretty much non-existent.

We still don't know what causes DOMS. If we don’t know what causes something, we probably don’t know how to cure it. An analysis of 12 studies found that stretching before, during or after exercise did not significantly reduce DOMS. Any benefit derived from stretching is an increase in pain tolerance. An increase in pain tolerance might help mask some of the symptoms of soreness, and this might be of psychological help.

The only way to deal with soreness is to do more of that which got you sore. According to the repeated bouts effect, the more adapted you are to an exercise, the less damage it causes. This explains why performing an exercise for the first time or training at an intensity you’re not used to leaves you sore and wanting to curl up in bed all day.

Bottomline: Stretching doesn’t prevent soreness. Get used to it.

D. I stretch to prevent injury.

I’ve said it once and I’ll say it again - you cannot prevent an injury, you can help mitigate it. The most common tennis injuries tend to be chronic overuse injuries especially tendinopathies (chronic tendon problems). Tendons are tough bands of tissue that connect muscles to bones. In tennis, tendons play a key role in storing and releasing elastic energy in the form of the Stretch-Shortening Cycle (SSC). Tennis places extreme stress on your tendons and more compliant tendons absorb energy better, leading to less stress being placed on them, hence lessening the risk of injury. The question is whether static stretching can decrease tendon stiffness/increase compliance.

Only two studies have looked at the effects of stretching on tendon stiffness and both have found no effect as a result of static stretching. By contrast, ballistic stretching has been demonstrated to decrease tendon stiffness. On the other hand, eccentric training plays an important role in injury prevention and has been shown to be an effective treatment for tendinopathy.

Static stretching resulted in a significant decrease of the passive resistive torque, but there was no change in Achilles tendon stiffness. In contrast, ballistic stretching had no significant effect on the passive resistive torque of the plantar flexors. However, a significant decrease in stiffness of the Achilles tendon was observed in the ballistic-stretch group. (Mahieu NN, McNair P, De Muynck M, Stevens V, Blanckaert I, Smits N, Witvrouw E 2007)

A further case for eccentric training is its ability to increase muscle fibre length. Muscle fibres are comprised of small contractile units called sarcomeres. Strength training with eccentric contractions (actively lengthening a muscle under load) have been shown to promote sarcomerogenesis/increased muscle fibre length. Conversely, there is insufficient evidence to show that static stretching can increase the number of sarcomeres (sarcomerogenesis) and more research is needed.

Is tightness really a bad thing?

Not only is the relationship between tightness and injury risk weak, tightness can also prevent you from getting injured. Any sport performed at a high level is going to result in imbalances with some muscles being overused, others underused; some shortened, others lengthened; some strong, others weak. In such cases, tightness serves as a protective mechanism and not as a limitation. Tightness helps keep the joint stable. Your nervous system can also tighten up a weak muscle to prevent it from getting injured at longer lengths. Doing long-duration static stretching is going to run you the risk of making the joint more unstable and exacerbating the imbalance. Strength training seems to be the best way to introduce strength, stability and mobility to the area.

Stretching can even cause injuries. It is pretty common to see hyper-mobile athletes who possess pathologically greater-than-average ranges of motion. It is even more common to hear such athletes complain of tightness, and develop a penchant for stretching as a result. While it may look cool to bring your thumb and forearm together, joint laxity can predispose you to sprains, dislocations, stress fractures and even anxiety attacks, and stretching just continues the vicious cycle.

Finally, over-stretching, i.e. - forcing your joints and muscles into greater ranges that they can tolerate, runs you the risk of spraining (joints) and straining them (muscles).

Bottomline: In the words of GW. Gleim and MP.McHugh,

There is no scientifically based prescription for flexibility training and no conclusive statements can be made about the relationship of flexibility to athletic injury. The literature reports opposing findings from different samples, frequently does not distinguish between strain, sprain and overuse injury, and rarely uses the proper denominator of exposure.

Flexibility is a poor predictor of injury risk. How flexible you need to be depends on your current flexibility and what your sport calls for. Strength is a much better predictor of injury and strength training seems to be the closest thing we have to a miracle drug. Strength training increases the ability of our muscles to withstand high stress, teaches our joints to remain stable even in extreme positions and even improves flexibility.

Flexibility can be maintained or improved by exercise modalities that cause more robust health benefits than stretching (e.g., resistance training) - James Nuzzo

Exception: Stretching might be useful in preventing or restoring loss of joint ROM post injury and maybe be recommended as rehab. This is very specific to the injury and is a topic for another post.

Why I stretch?

Simply put, it feels good. If something feels good, it must have also done you good, right? Not really. A six hundred calorie serving of cheesecake feels good but you know it doesn’t do you much good. The profound point I’m trying to make is that it’s important to understand where stretching lies in the “feel-good, do-good” continuum. I stretch having made peace with the fact that stretching is neither a magic pill nor a cyanide capsule. It is ridiculous to think that I would stretch knowing how little it does, but that probably says more about how stretching is culturally ingrained in us, and how fanatically the stretching dogma is perpetrated.

And that’s a stretch…

Stretching elicits mainly neurological and some mechanical changes. Stretching is about teaching your nervous system to tolerate the elongated position. In a way we get used to stretching, and modify the way we perceive discomfort. Any increase in muscle extensibility is transient and can be attributed to modification in your pain tolerance/ subjective appraisal of pain. It’s hard to give up stretching without getting emotional or philosophical. You can stretch to feel better as long as you don’t form a hedonistic relationship with it.

Aum.